Heat treatment and characterization of high entropy alloy (HEA) thin films fabricated by cathodic arc deposition

Abstract

This thesis mainly studied the effect of heat treatment on the AlCrFeCoNiCu0.5 thin films with different phases fabricated by cathodic arc deposition due to three reasons. Firstly, cathodic arc deposition for the synthesis of HEA thin films has been rarely researched before, and more breakthroughs need to be achieved. Secondly, the application fields of metals and alloys are closely related to thermal stability and high-temperature oxidation resistance. Additionally, the mechanical properties of HEA thin films, such as hardness and elastic modulus, may be improved by annealing. The research works involved in this thesis were completed by using various characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation.

The thermal stability of face-centered cubic (FCC) structured-AlCrFeCoNiCu0.5 thin films was firstly investigated by 500 °C-vacuum annealing with different time. In addition, the HEA thin films with single FCC phase were atmospherically annealed at different temperatures for 5 hours to further explore the thermodynamic behavior and oxidation resistance at elevated temperature, and optimize the mechanical properties. Furthermore, the influence of vacuum heat treatment on the HEA thin films consisting of dual phases was also studied in detail. The evolution of microstructure and the changes in mechanical properties were clearly exhibited and systemically discussed in chapter 4-6. In summary, all the research outcomes performed in this thesis not only are beneficial to deepen the understanding of HEA thin films, but also provide valuable experience for future design and optimization of the related materials.